This invention relates to injection of pressurized materials through a manifold, such as injection molding of plastic melt in a hot runner system. More specifically, this invention relates to an improved injection molding hot runner system in which the rate of melt flow is controlled through the gate during an injection molding cycle.
U.S. Pat. No. 5,556,582 discloses a multi-gate single cavity system in which the rate of melt flow through the individual gates is controlled independently via a control system according to specific target process conditions. This system enables the weld line of the part (the section of the part in which the melt from one gate meets the melt from another gate) to be selectively located. It also enables the shape of the weld line to be altered to form a stronger bond.
The ""582 patent discloses controlling the rate of melt flow with a tapered valve pin at the gate to the mold cavity. It also discloses placing a pressure transducer inside the mold cavity. Placing the pressure transducer inside the mold cavity can result in the pressure transducer sensing pressure spikes which can occur when the valve pin is closed. A pressure spike sensed by the transducer can cause an unintended response from the control system, and result in a less precise control of the melt flow than desired.
The control system disclosed in the ""582 patent uses the variables of valve pin position and cavity pressure to determine what position the valve pin should be in. Thus, the algorithm performed by the control system in the ""582 patent utilizes two variables to control the rate of melt flow into the cavity.
An injection molding apparatus and system are provided in which the rate of material flow during the injection cycle is controlled. According to one preferred embodiment, an injection molding system is provided that includes an injection molding machine including a hydraulic power source, a manifold for distributing material injected from said injection molding machine to a plurality of gates leading to one or more mold cavities, and a controller to individually control respective rates at which material is injected through said gates during an injection cycle. The controller is coupled to the hydraulic power source and the hydraulic power source supplies hydraulic power to both the injection molding machine and to control said respective rates.
According to another embodiment, an injection molding system is provided that includes an injection molding machine, and a manifold for distributing material injected from said injection molding machine to a plurality of gates leading to one or more mold cavities. The injection molding machine includes a controller to individually control respective rates at which material is injected through said gates during an injection cycle.
According to another embodiment, an injection molding system is provided that includes an injection molding machine, a manifold for distributing material injected from a nozzles of said injection molding machine to a plurality of gates leading to one or more mold cavities, a controller to individually control respective rates at which material is injected through said gates during an injection cycle, and a pressure transducer coupled to the nozzle of said injection molding machine. The controller receives pressure data from the pressure transducer.
According to another embodiment, an injection molding system is provided that includes an injection molding machine, a manifold for distributing material injected from a plurality of nozzles of said injection molding machine to a plurality of gates leading to one or more mold cavities, a controller to individually control respective rates at which material is injected through said gates during an injection cycle, and a position transducer coupled to a screw of said injection molding machine. The controller receives position data of the screw from the position transducer.
According to another embodiment, an injection molding system is provided that includes an injection molding machine, a hot runner including a manifold and a plurality of injection nozzles for distributing material injected from said injection molding machine to a plurality of gates leading to one or more mold cavities, a controller to individually control respective rates at which material is injected through said gates during an injection cycle, and at least one pressure transducer mounted in the one or more cavities, the pressure transducer coupled to the controller to send pressure data to the controller. The controller alters the at least one respective rate from an injection pressure to a pack pressure when the pressure transducer detects a predetermined pressure value.
According to another embodiment, an injection molding system is provided that includes an injection molding machine, a hot runner including a manifold and a plurality of injection nozzles for distributing material injected from said injection molding machine to a plurality of gates leading to one or more mold cavities, a controller to individually control respective rates at which material is injected through said gates during an injection cycle, and at least one pressure transducer mounted in the one or more cavities, the pressure transducer coupled to the controller to send pressure data to the controller. The controller determines an end of the pack period of the injection cycle for at least one respective rate when the pressure transducer detects a predetermined pressure value.
According to another embodiment, an injection molding system is provided that includes an injection molding machine, a hot runner including a manifold and a plurality of injection nozzles for distributing material injected from said injection molding machine to a plurality of gates leading to one or more mold cavities, a plurality of pressure transducers coupled to said hot runner for sensing material pressure flowing to said gates, and at least one pressure transducer mounted in the one or more cavities, the pressure transducer to sense the material pressure inside the one or more cavities.